It has been known for some time that the yield of hydrocarbons, such as gas and petroleum, from wells can be increased by fracturing the formation so as to stimulate the flow of hydrocarbons in the well. Various formation fracturing procedures have been proposed and many now are in use. Among these procedures are treatments with various chemicals (usually acids in aqueous solutions), hydraulic fracturing in which liquids are injected under high pressure (usually with propping agents), explosive methods in which explosives are detonated within the formations to effect mechanical fracture, and combinations of the above procedures.
Chemical treatments usually involve the use of large volumes of chemicals which can be expensive and difficult to handle, and which pose problems of contamination and disposal. Hydraulic fracturing ordinarily requires that large volumes of liquids be made available at the well site and that equipment be made available for handling these large volumes of liquid. Again, there can be disposal problems, as well as contamination of the well. Explosive methods can be exceptionally hazardous from the standpoint of transporting and using the necessary explosives. These methods also present difficulties in controlling the effects of such a procedure.
Other suggestions for increasing the yield of existing wells entail heating the formation to induce the flow of hydrocarbons from the formation. Methods and apparatus have been developed by which various combustion devices have been lowered into the borehole of a well to attain heating of the formation adjacent the device. The effectiveness of such devices is limited by the necessity for fitting the devices into a borehole and then obtaining only more-or-less localized effects.
A combustion method designed to stimulate the well through mechanical fracture is known as controlled pulse fracturing or high energy gas fracturing. A good description of this method appears in an article by Cuderman, J. F., entitled "High Energy Gas Fracturing Development," Sandia National Laboratories, SAND 83-2137, October 1983. Using this method enables the multiple fracturing of a formation or reservoir in a radial manner which increases the possibility of contacting a natural fracture. Unfortunately, these radial fractures often do not penetrate deeply enough into the formation.
Slusser in U.S. Pat. No. 4,109,721 issued on Aug. 29, 1978 discusses a method of proppant placement during a hydraulic fracturing treatment. Via this method, a first proppant pack was deposited in the lower portion of a fracture. Afterwards, a slug of fracturing fluid liquid containing fluid loss additives was injected into the formation to deposit the fluid loss additives along the upper leading edge of the proppant pack. This provided a seal along the upper edge of the proppant pack. Thereafter, a high filter loss fracturing fluid, containing proppants, with no fluid loss additives was injected into the formation at a pressure to extend the fracture further.
During hydraulic fracturing when a proppant is utilized the fracturing fluid must be selected to allow the proppant to remain suspended until said fracturing treatment is completed which may require several hours. Because there is a time interval between the hydraulic fracturing treatment and the injection of the fluid containing the proppants, often sufficient proppant does not enter the desired fracture.
Therefore, what is needed is a method which will provide for proppant placement within fractures upon the initiation of said fractures thereby allowing for increased amounts of proppant placement within said fractures.